Hours before his highly anticipated meeting with Chinese leader Xi Jinping in Korea, President Trump went on social media to take aim at a different target: ex-FBI agent Walter Giardina. 

“Walter Giardina is a DIRTY COP! He should be, along with Deranged Jack Smith, the sinister team of Lisa Monaco and Andrew Weissmann, Liddle’ Jay Bratt, Norm Eisen and his FAKE Charity, CREW, Christopher Wray, Merrick Garland, Thomas Windom, who dreamt up the corrupt J-6 Witch Hunt, should be investigated immediately,” Mr. Trump wrote on Truth Social. “They are a disgrace to our Nation.”

Mr. Trump, from 7,000 miles away, was responding to news that Senator Chuck Grassley, a Republican of Iowa, had released more than 1,700 pages of records that laid out in painstaking detail how the then-special prosecutor, Jack Smith, sent 197 subpoenas targeting more than 430 Republican and conservative organizations and individuals, two of Mr. Trump’s most trusted advisers, Dan Scavino and Stephen Miller. 

Among the materials Mr. Smith requested as part of the investigation, codenamed “Arctic Frost,” included his targets’ communications with media companies like Fox News, CBS, Sinclair, and Newsmax.

Mr. Giardina’s name appears in more than 100 of Mr. Smith’s “Arctic Frost” subpoenas, which Mr. Grassley posted online Wednesday.

“Arctic Frost was the vehicle by which partisan FBI agents and DOJ prosecutors could improperly investigate the entire Republican political apparatus,” Mr. Grassley said during a press conference Wednesday.

“If this happened to the Democrats, they’d be as rightly outraged as we are.”

In response, Senator Eric Schmitt, a Republican of Missouri, called for a series of “Watergate style hearings.”

“If we’re ever going to root this out, we have to be serious about it, and consequences have to follow: resignations, firings, criminal prosecutions. You simply can’t in this country use the justice system to throw people in jail because they have a red jersey on or a blue jersey on,” Mr. Schmitt told reporters Wednesday.

An attorney for Mr. Smith, Lanny Breuer, said in a statement that his client was “happy to discuss his work as Special Counsel and answer any questions at a public hearing just like every other Special Counsel investigating a president before him has done.”

“We hope the House and Senate Judiciary Committees will agree so the American people can hear directly from him. Name the time and place. Jack will be there.”

In May, Mr. Grassley released a trove of internal emails from Mr. Giardina and other FBI agents involved in the arrest of Peter Navarro – a top Trump aide who was sentenced to four months in prison for refusing to testify before the Democrat-controlled January 6 committee –  describing the emails as evidence of longstanding “political rot” within the bureau. 

“Instead of focusing on the rampant cases of murder and rape perpetrated against everyday Americans, personnel in the FBI’s Washington Field Office and D.C. U.S. Attorney’s Office were obsessing over ways to target President Trump and his allies. Their conduct is disgraceful and un-American,” Mr. Grassley said in May.

Mr. Giardina, who was a key partner with federal prosecutors in their investigations of Mr. Trump, was fired in August due to his role  in the Justice Department’s Trump probes during the Biden Administration. In his termination letter to Mr. Giardina, the FBI director, KashPatel, said the special agent “exercised poor judgement and a lack of impartiality in carrying out duties, leading to the political weaponization of the government.”

Weeks before his firing, Mr. Giardina’s wife, Colleen, died of pancreatic cancer. 

A lawsuit filed by three former high-ranking FBI officials against Mr. Patel and Attorney General Pam Bondi claims that the FBI’s co-deputy director, Dan Bongino,  pressured the head of the Washington Field Office to fire Giardina who in 2022 had arrested Mr. Navarro at a Washington airport on contempt of Congress charges. Mr. Navarro, then 74, served four months in prison for refusing to cooperate with the January 6 committee. Mr. Navarro at the time called Mr. Giardina and another special agent “kind Nazis.”  

The head of Washington Field Office, Steve Jensen, pushed back at Mr. Bongino’s order to fire Mr. Giardina, a military veteran and a longtime FBI special agent who was protected by “certain rights.”

“He explained that Bongino would likely be deposed in a lawsuit should Giardina choose to challenge his unlawful firing. Bongino did not pursue further his demand that Giardina be summarily fired in that meeting,” the lawsuit alleged. 

But in early August of this year, Mr. Patel fired Mr. Giardina and Mr. Jensen, among other senior, longtime FBI officials,